Glucose oxidase (GOD) is an enzyme which catalyzes the following reaction: ##STR1## This enzyme is currently obtained mainly from Aspergillus Niger and is used in various applications such as the removal of oxygen (for example from foods) and in determination methods for glucose (in biological liquids, foods etc.). Other useful sources of GOD include Penicillum organism such as Penicillum notatum. As in the case of all enzymes, GOD is poorly stable, and therefore for commercial purposes formulations of solid or liquid type are generally used, depending on the type of application for which the enzyme is intended.
Formulations of the liquid type are easier to produce than solid formulations, but the enzyme is less stable and the preparation has therefore a shorter shelf life.
Various efforts have therefore been made in the past to overcome the drawback of excessive instability of the enzyme in liquid form. The literature on this subject includes for example Fieschl J. et al., Clin. Chem. 21, 6, 760-761 (1975), the patent CH 664,160 A5 and Boehringer Mannheim Technical Bullentin EC.1.1.3.4, proposing the use of various stabilizing substances to added to liquid GOD preparations, such as non-ionic surfactants or sodium chloride.
In addition current liquid GOD preparations generally contain a buffer in a concentration adequate to stabilize the solution pH. A phosphate buffer is the one most commonly used in reagent formulations normally employed for determining glucose in biological liquids.